Device for warming and moistening gases having both an active and passive heat exchanger.

ABSTRACT

A device for heating and moistening respiratory gases with a small volume of dead space which is especially suitable for giving artificial respiration to premature and newborn infants and children. This device includes three parts, whereby two parts, largely made of metal, are interconnected in a housing and form a connecting component combined with an active steam-sterilizable moistening and heating device into which a third part, a one-time heating-moistening exchanger insert, is fitted. The upper third of this insert acts as a passive heat-moisture exchanger which premoistens and preheats the dry respiratory gas on inspiration (about 30° C., 100% relative humidity) and the central and lower third of which, supported by the active moistening device and heating with the aid of the active heat-moisture device, finally undertakes the optimum conditioning of the respiratory gas (36-37° C., 100% r.h.). On expiration, 60-80% of the moisture and heat of the optimally warm and damp respiratory gas is recovered by the heat-moisture exchanger insert primarily via its upper third away from the patient. In cases of great respiratory difficulty, e.g. in very small premature infants, the volume of dead space of the device can be reduced still further by opening an air outlet stub in the third part.

FIELD OF THE INVENTION

The invention relates to an apparatus for warming and moistening gases,more particularly, breathing gases during artificial respiration,comprising the combination of at least one passive heat and moistureexchanger and at least one active warming and moistening device.

BACKGROUND OF THE INVENTION

Under physiological conditions, the nose functions to provide activewarming and heating of breathing air. When a patient is undergoingartificial respiration however the nose is shunted by a flexible tube,whose end is inserted into the trachea. The moistening and warmingaction on the breathing gases, which is absolutely essential for normalfunction of the lungs, is presently performed by an apparatus, whichmore particularly operates in accordance with two principles. A firstpart of the apparatus actively imparts heat and moisture to the air. Inthis case for instance dry, cold air is caused to pass through anelectrically heated water bath moistener and thereby conditioned priorto being supplied to the patient. A second part of the apparatusoperates passively as a heat and moisture exchanger (H. M. E.). In thiscase heat and moisture are removed from the moist, warm expired air andare then imparted to the cold, dry air to be inspired without anadditional active supply of heat and moisture from the surroundingstaking place.

In accordance with this prior art it is admittedly possible for theapparatus to supply sufficiently tempered and moistened respiratory airwhen there is an active supply of heat and moisture, but however veryinvolved technical and nursing measures are necessary so that productionand running costs of such equipment are very high. In contradistinctionto such apparatus, there are less complex, simply designed and simplyoperated passive heat and moisture exchangers, but they have not so farprovided a sufficient moistening and warming action for artificialrespiration.

In an earlier application, see European patent publication 0 413 127 A2,the applicant has described an apparatus for warming and moisteningbreathing air for artificial respiration of the type initially mentionedin the case of which the above mentioned advantages are obtained by acombination of independent passive heat and moisture exchangers with anactive heat and moisture exchanger. However, this prior art device isrelatively complex in design. Furthermore, such a device involved someproblems owing to there being an excessive dead volume, which due to there-inspiration of exhaled air had a particularly pronounced effect inthe case of newly born babies, owing to their small vital capacity.

SUMMARY OF THE INVENTION

One object of the present invention is accordingly to provide anapparatus of the type initially mentioned which optimally suppliesmoistened breathing air with small dead volumes and in this respect isvery simple in design and is simple to operate.

In accordance with the invention, a heat and moisture exchanger insertis provided mounted in a housing and one part operates as a passive heatand moisture exchanger and another part operates as an active heat andmoisture exchanger with the heating and moistening device surroundingit. This means that there is a single unit comprising both a passiveheat and moisture exchanger and an active heating and humidifyingdevice. The advantages of both principles are consequently realized in aconstructionally compact design as a simple apparatus so that on onehand there is optimum moistening and heating of the breathing gaseswhile at the same time there is a low degree of technical complexity,little nursing attention is required, while costs are low.

In accordance with a further advantageous development of the invention,the apparatus is so designed that its housing is divided into two parts,an upper housing part being in the form of a conical connecting partwith a cylindrical cavity to receive the passive heat and moistureexchanger insert or cartridge and a lower housing part being in the formof an active moistening and heating device, into which an adapter can bereceived for the tube which is to be inserted into the patient.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages of the invention will be understood from thefollowing detailed descriptive disclosure of one embodiment illustratedin the accompanying drawings.

FIG. 1 is a perspective, exploded view of the working embodiment whichis made in three parts.

FIG. 2 shows a section in an exploded view taken along the line II--IIof FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The apparatus in accordance with the invention comprises three parts,including a connecting member part 1 and a heating connecting part 2fabricated mostly of metal and being permanently connected with oneanother.

The part 1 constitutes a connecting member for a Y adapter or therespiration head of an artificial respiration flexible tube system, viawhich the breathing gases are supplied during the inhalation phase andare abducted in the exhalation phase. This connecting member 1 isdesigned in the form of a metallic cylindrical tube or hollow cylinder,which on the outside is provided with a standardized connection cone.Before use, a snugly fitting cylindrical heat and moisture exchangerinsert 3 is introduced into its lumen, which contains an exchangemedium, such as, for example, a commercially available H. M. E. asproduced by the Company ICOR AB of Sweden, so that a lowermost edge 5 ofthe insert 3 abuts the cruciform internal fitting 4. Four metal tubelets6 extend from and perpendicular to fitting 4. The tubelets 6 terminatein tips with lateral openings 7. The ends of the tubelets extend intothe center third of the heat and moisture exchanger insert 3 and supplythe insert 3 with exactly metered tempered sterilized water, which issupplied to the tubelets via an external, known metering device by wayof flexible tube ports 10, an annular channel 9 and the fine tubes 8 ofthe cruciform internal fitting 4. The annular channel 9 is connected viaits metallic casing 11 in a thermally conductive manner with the heatingconnecting part 2 of the apparatus. The heating element 12 installed inpart 2 and the two temperature sensors 13 and 14 are supplied via anexternal connecting cable and a multi-pin plug 15 with electrical powerfor exact monitoring and control. The synthetic resin casing 16 servesfor heat insulation of the heating part 2, whereas the standardizedinner cone 17 serves for a reliable and simultaneously releasableconnection of the inserted tube adapter 18 with the standardizedexternal cone 19. The port 23 is shut off by a removable cap 24. Ashallow cavity 25 is formed between the tube adapter 19 and a lower sideof the cruciform internal fitting 4 when the tube adapter 19 is insertedinto cone 17. The port 23 connects cavity 25 and the area surroundingthe apparatus.

A description will be provided of the operation of the inventionexplained with reference to a working embodiment. Dry, cold breathinggas (at approximately 20° C. with a relative humidity of approximately10%) passes during the inhalation phase from an artificial respirator,not illustrated in the drawing, via the patient flexible tube systemwith a Y adapter secured to the connecting member 1. Thence thebreathing gas flows through the heat and moisture exchanger insert 3 (H.M. E. insert or cartridge). In its upper third, the insert 3overwhelmingly functions as a passive H. M. E., in which cold breathinggas is passively warmed in a first stage and is pre-humidified by storedheat and moisture, which have previously been abstracted from theexhaled air of the patient on which artificial respiration is beingperformed. The breathing gas will however here only attain a temperatureof approximately 30° C. at 100% relative humidity. For this reason in asecond stage in the center and lower thirds of the H. M. E. insert,active post-moistening and post-heating of the breathing air areperformed with the result that via the center lumen 21 and 22 of theflexible tube adapter 18 and through a tracheal tube slipped onto thecone 20, the air will then reach the trachea of the patient at atemperature of 36 to 37° C. at 100% relative humidity. This activepost-moistening and post-heating is performed in such a manner that byusing an external controller, exactly metered water and electricalheating power is supplied to the above mentioned device. This will leadto heating of the metal parts of the apparatus, more particularlyhowever, owing to the additional emergence of heated water via thetubelets 6 into the central third of the H. M. E. insert 3 and thencerapidly spreading out owing to the action of gravity into the lowerthird of the insert 3 so that active heating and moistening take place.Owing to the large surface area of the H. M. E. insert, rapid andoptimum conditioning of the passing through air to be inhaled isensured.

In the exhalation phase the moist gas to be inhaled flows at bodytemperature (i.e. at 36 to 37° C. at 100% relative humidity) via theflexible tube, first into the tube adapter 18 and then into the activelyhumidified and warmed lower two thirds of the H. M. E. insert 3 to giveup only a little of its total heat and moisture and then in the upperpassive third thereof 60 to 80% of its total heat and moisture. Thismeans that in the flexible tube system only a very small quantity ofmoisture changes into condensate. In comparison with conventionalsystems there is the additional advantage of economy in nursingattention but furthermore advantages relevant to bacteriological andhygienic aspects.

Since in the apparatus in accordance with the invention the part whichis technically most complex, that is to say the connected parts 1 and 2,may be produced in the form of a readily cleaned, steam sterilizable,combined active warming and moistening device with a connecting member,during use there is not only an optimum conditioning of the breathinggases for the patient, but furthermore protection against infection andsaving in costs. Owing to the incorporation of two temperature sensorswith a following twin-channel electronic temperature monitoring meansand controller, and heating of the moistening device to a temperatureonly slightly above body temperature and with only a small heatcapacity, it is possible for reliable artificial respiration of thepatient to take place without excessively heated breathing gases evenwhen operating under extreme conditions. Moreover owing to the smalldead volume, objectionable re-inspiration of exhaled air is not to befeared in the case of babies and children. In particularly difficultartificial respiration situations, as for instance in artificialrespiration of premature babies with high respiration rates and smallvital capacities it is possible to arrange for a further reduction infunctional dead volume by opening the venting port 23 by removal of theclosure cap 24. The spent, exhaled air thereby passes via the cavity 25and the port 23 opening thereinto directly into the surroundings.

I claim:
 1. An apparatus for warming and moistening gases, moreparticularly breathing gases during artificial respiration, includingthe combination of at least one passive heat and moisture exchanger andat least one active warming and moistening device, said apparatuscomprising:a housing, a heat and moisture exchanger insert mounted insaid housing and operating as a passive heat and moisture exchanger andas an active heat and moisture exchanger, said housing including a firsthousing part having an annular channel and a second housing part with acruciform insert arranged between said first housing part and saidsecond housing part, said cruciform insert including channels connectedwith said annular channel of said first housing part and said cruciforminsert having tubelets in communication with said annular channel, saidtubelets having open ends communicating with said heat and moistureexchanger insert.
 2. The apparatus as claimed in claim 1, wherein saidfirst housing part is a conical connecting part with a cylindricalcavity for receiving said heat and moisture exchanger insert and saidsecond housing part is an active moistening and heating device.
 3. Theapparatus as claimed in claim 1, wherein said open ends of said tubeletsextend into a center third of said heat and moisture exchanger insert.4. The apparatus as claimed in claim 1, wherein said cruciform insertincludes arms extending between said tubelets and said annular channel.5. The apparatus as claimed in claim 1, wherein said first and saidsecond housing parts are made of metal and are at least partly coveredwith a thermally insulating synthetic resin casing.
 6. The apparatus asclaimed in claim 1, wherein a flexible tube adapter is inserted intosaid second housing part.
 7. The apparatus as claimed in claim 1,wherein said second housing part includes a venting port connected withthe surroundings and said venting port is closed by a removable cap.